Grass trimmer

ABSTRACT

A grass trimmer includes a trimming head, a driving device for driving the trimming head to rotate so as to cut vegetation and an operating device for a user to operate so as to control the driving device. The trimming head includes a spool and a line holding element, the spool is used to wind a trimming line, and the line holding element is formed with a line holding structure. The driving device includes a motor. The grass trimmer has an auto-winding mode. In the auto-winding mode, the motor drives at least one of the spool and the line holding element to make the spool and the line holding element rotate relatively so that the trimming line is wound on the spool automatically.

RELATED APPLICATION INFORMATION

This application is a continuation-in part of U.S. application Ser. No.17/061,584, filed Oct. 2, 2020, which is a continuation of U.S.application Ser. No. 16/363,609, filed Mar. 25, 2019, which is acontinuation of U.S. patent application Ser. No. 15/839,257, filed Dec.12, 2017, which claims the benefit of International Application NumberPCT/CN2016/110351, filed on Dec. 16, 2016, through which thisapplication also claims the benefit of Chinese Patent Application No.201610044465.6, filed on Jan. 22, 2016, Chinese Patent applicationnumber 201610626524.0, filed on Aug. 1, 2016, and Chinese Patentapplication number 201610875071.5, filed on Oct. 7, 2016, each of whichis incorporated herein by reference in its entirety.

FIELD OF THE DISCLOSURE

The present disclosure relates generally to grass trimmers and, moreparticularly, to a grass trimmer having an auto-winding mode, anoperating method thereof and a control method thereof.

BACKGROUND OF THE DISCLOSURE

Grass trimmers are a kind of gardening tools, which are used to trim thelawn. The grass trimmer includes a trimming head. The trimming headrotates at high speed to drive a trimming line mounted thereon to rotateso as to realize the cutting function.

The trimming head includes a spool allowing the trimming line to windthereon. During the cutting operation, the trimming line is worn awaygradually due to wear. After operating for a period, it is needed tochange a new trimming line and wind the new trimming line around thespool. For the currently known trimming line, a user needs to rotate thespool manually to wind the trimming line around the spool. The windingoperation is inconvenient and the winding speed is slow.

The statements in this section merely provide background informationrelated to the present disclosure and may not constitute prior art.

SUMMARY

In one aspect of the disclosure, a grass trimmer is provided. The grasstrimmer includes a trimming head, a driving device for driving thetrimming head to rotate so as to cut vegetation and an operating devicefor a user to operate so as to control the driving device. The trimminghead includes a spool and a line holding element, the spool is used towind a trimming line, and the line holding element is formed with a lineholding structure allowing the trimming line to pass or bypass. Thedriving device includes a motor, the grass trimmer has an auto-windingmode, in the auto-winding mode, the motor drives at least one of thespool and the line holding element to make the spool and the lineholding element rotate relatively so that the trimming line is wound onthe spool automatically.

In another aspect of the disclosure, an operating method for winding atrimming line of a grass trimmer is disclosed. The operating methodincludes:

providing the grass trimmer, the grass trimmer including a spoolallowing the trimming line to be wound thereon, a line holding elementbeing formed with a line holding structure, and a motor being capable ofdriving at least one of the spool and the line holding element;

associating the trimming line with the line holding element andinserting the trimming line in the spool; and

starting the motor to make the spool and the line holding element rotaterelatively.

In another aspect of the disclosure, an operating method for winding atrimming line of a grass trimmer is disclosed. The operating methodincludes:

associating the trimming line with a line holding element disposed onthe grass trimmer and inserting the trimming line in a spool disposed onthe grass trimmer; and

starting a motor to make the spool and the line holding element rotaterelatively.

In another aspect of the disclosure, a control method for winding atrimming line of a grass trimmer is disclosed. The grass trimmerincludes a spool allowing the trimming line to be wound thereon, a lineholding element being formed with a line holding structure for holdingthe trimming line and a motor being capable of driving at least one ofthe spool and the line holding element to make the spool and the lineholding element rotate relatively. The control method includes supplyingpower to the motor to make the spool and the line holding element rotaterelatively.

Further areas of applicability will become apparent from the descriptionprovided herein. It should be understood that the description andspecific examples are intended for purposes of illustration only and arenot intended to limit the scope of the present disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a schematic view of an exemplary grass trimmer.

FIG. 1B a schematic view showing the structure of a part of the grasstrimmer in FIG. 1A.

FIG. 1C is an exploded view of the structure in FIG. 1B.

FIG. 1D is a schematic view showing the transmission of a spool and ahead housing in FIG. 1B.

FIG. 2A is an exploded view of an exemplary trimming head and anexemplary damping device.

FIG. 2B is a section view of the trimming head and the damping device inFIG. 2A.

FIG. 3A is also a schematic view of an exemplary trimming head and anexemplary damping device.

FIG. 3B is a schematic view showing the transmission of a spool and ahead housing in FIG. 3A.

FIG. 4A is also a schematic view of an exemplary grass trimmer.

FIG. 4B is a schematic view showing the structure of a part of the grasstrimmer in FIG. 4A.

FIG. 4C is a section view of the structure in FIG. 4B.

FIG. 4D is an exploded view of the structure in FIG. 4B.

FIG. 4E is another exploded view of the structure in FIG. 4B.

FIG. 4F is a section view of an upper cover in FIG. 4E.

FIG. 4G is a section view of a spool in FIG. 4E.

FIG. 4H is a schematic view showing the inserting method of a trimminghead in FIG. 4A.

FIG. 4I is a schematic view of an operating device in FIG. 4A.

FIG. 4J is another schematic view of the operating device in FIG. 4A,wherein a first operating element and a second operating element are ina first preset operating state and a second preset operating staterespectively.

FIG. 4K is a schematic view of an operating device.

FIG. 4L is a schematic view showing a second operating element of theoperating device in FIG. 4K, wherein the second operating element is ina second position.

FIG. 4M is a schematic view of a line breaking device.

FIG. 5A is also a schematic view of an exemplary grass trimmer.

FIG. 5B is a schematic view of a trimming head and a first housing ofthe grass trimmer in FIG. 5A.

FIG. 5C is a schematic view of the trimming head and the first housingin FIG. 5B, wherein the trimming head and the first housing areseparated.

FIG. 5D is an exploded view of the structure in FIG. 5B.

FIG. 5E is another exploded view of the structure in FIG. 5B.

FIG. 5F is a plane view of the structure in FIG. 5B.

FIG. 5G is a sectional view of the structure cut along line A-A in FIG.5F.

FIG. 5H is a schematic view of a spool and a positioning element in FIG.5D.

FIG. 5I is a schematic view of a lower cover in FIG. 5D.

FIG. 5J is a schematic view of the trimming head in FIG. 5F, wherein thetrimming head is moved upwardly relative to the first housing.

FIG. 5K is a sectional view of the structure cut along line B-B in FIG.5J.

FIG. 5L is a schematic view of a damping device in FIG. 5A.

FIG. 5M is a schematic view of the first housing and a driving shaft inFIG. 5C.

FIG. 5N is a sectional view of the structure cut along line C-C in FIG.5M.

FIG. 5O is an exploded view of the damping device in FIG. 5A.

FIG. 5P is a plane view of the damping device in FIG. 5A, wherein astopping element of the damping device is at a stopping position.

FIG. 5Q is a sectional view of the structure cut along line D-D in FIG.5P.

FIG. 6A is a schematic view of a trimming head, a motor and a dampingdevice.

FIG. 7A is a schematic view of an electric magnet and a trimming head.

FIG. 7B is a schematic view of a head housing in FIG. 7A, wherein thehead housing is moved relative to a spool.

FIG. 8A is a schematic view of a head housing, wherein the head housingcan be pulled by a rope.

FIG. 8B is a schematic view of the head housing in FIG. 8 a , whereinthe head housing is moved relative to a spool.

FIG. 8C is another schematic view of a head housing, wherein the headhousing can be pulled by a rope.

FIG. 8D is a schematic view of the head housing in FIG. 8C, wherein thehead housing is moved relative to a spool.

FIG. 9A is a circuit block diagram of a grass trimmer using a brushlessmotor.

FIG. 9B is a schematic view of a driving circuit in FIG. 9A.

FIG. 9C is a circuit block diagram of a grass trimmer using a brushmotor.

FIG. 10A is a schematic view of the second operating element disposed ona connecting rod assembly.

FIG. 10B is a schematic view of the second operating element disposed onthe first housing.

FIG. 10C is a schematic view of the second operating element disposed ona guard.

FIG. 11A is a schematic view of a grass trimmer having a line holdingelement.

FIG. 11B is a schematic view of a head housing and a spool of the grasstrimmer in FIG. 11A, wherein the head housing and the spool areseparated.

FIG. 11C is a plane view of the structure in FIG. 11A.

FIG. 11D is a schematic view of an exemplary line holding element.

FIG. 12A is a schematic view of a trimming head and a line holdingelement acted as an attachment.

FIG. 12B is a schematic view of the line holding element in FIG. 12A,wherein the line holding element is in a working state.

FIG. 12C is a schematic view of a line frame element, wherein the lineframe element is driven by a motor.

FIG. 13A is a schematic view of an energy storing device, a motor and atrimming head.

FIG. 13B is an enlarged view of a part of the structure in FIG. 13A.

FIG. 14A is a flow diagram showing a control method for controllingwinding of a grass trimmer.

FIG. 14B is another flow diagram showing a control method for winding ofa grass trimmer.

FIG. 14C is a flow diagram showing an operating method for winding of agrass trimmer.

FIG. 15 a is also a schematic view of an exemplary grass trimmer.

FIG. 15 b is a cross-sectional view of the grass trimmer in FIG. 15 a.

FIG. 15 c is an enlarged view of a front end portion of the grasstrimmer in FIG. 15 b.

FIG. 15 d is an enlarged view of a rear end portion of the grass trimmerin FIG. 15 b.

FIG. 15 e is an exploded view of a front end portion of the grasstrimmer in FIG. 15 a.

FIG. 15 f is another exploded view of the front end portion of the grasstrimmer in FIG. 15 a.

The drawings described herein are for illustrative purposes only ofselected embodiments and not all possible implementations, and are notintended to limit the scope of the present disclosure. Correspondingreference numerals indicate corresponding parts throughout the severalviews of the drawings.

DETAILED DESCRIPTION

The following description of the preferred embodiments is merelyexemplary in nature and is in no way intended to limit the scope of theinvention hereinafter claimed, its application, or uses.

Referring to FIGS. 1A-1C, a grass trimmer 100 includes a trimming head110, a driving device 120 and an operating device 130.

The trimming head 110 is configured to mount and accommodate a trimmingline 101. The trimming line 101 is partially accommodated in thetrimming head 110. The trimming line 101 has a part extending out of thetrimming head 110 which is used to cut vegetation when the trimming head110 is rotated.

The driving device 120 is able to drive the trimming head 110 to rotateabout an axis 110 a so as to cut vegetation. The operating device 130 isused for a user to control the grass trimmer 100.

Specifically, the driving device 120 includes a motor 121 and a drivingshaft 122. The driving shaft 122 is connected with the trimming head 110so as to drive the trimming head 110 to rotate.

The grass trimmer 100 further includes a first housing 150, a secondhousing 160 and a battery pack 170. The first housing 150 is configuredto mount and accommodate the motor 121. The battery pack 170 acting as apower source at least can supply power to the grass trimmer 100. Thesecond housing 160 is configured to engage with the battery pack 170detachably.

A circuit board is accommodated in the second housing 160, which isconnected with the motor 121 electrically so that the battery pack 170can supply power to the motor 121 and control the motor 121. The firsthousing 150 and the second housing 160 are connected with each otherthrough a connecting rod assembly 190. The operating device 130 isfixedly mounted on the connecting rod assembly 190. The grass trimmer100 further includes an auxiliary handle 191 for the user to grip whichis fixedly mounted on the connecting rod assembly 190.

The trimmer head 110 includes a spool 111 and a head housing 112. Thespool 111 is accommodated in the head housing 112 for winding thetrimming line 101. The spool 111 is formed with an inner aperture 111 a.The head housing 112 is formed with an outer aperture 112 a. As anexample, the head housing 112 includes an upper cover 112 b and a lowercover 112 c, so that the head housing 112 is easy to assemble with thespool 111 and it is easy for the user to open the head housing 112 tocheck the inside of the head housing 112.

The trimmer head 110 includes a spring 113 which can apply a forcebetween the head housing 112 and the spool 111. The force applied by thespring 113 makes the spool 111 depart from the lower cover 112 c.

When it is needed to mount a new trimming line 101, the inner aperture111 a and the outer aperture 112 a are aligned, and then the trimmingline 101 is passed through the outer aperture 112 a and entered into theinner aperture 111 a. At this moment, as long as the spool 111 is movedrelative to the head housing 112, the trimming line 101 can be wound onthe spool 111 under the limiting action of the outer aperture 112 a. Thedriving shaft 122 is connected with the head housing 112, which candrive the spool 111 to rotate about the axis 110 a directly.

The spool 111 is connected rotatably with the head housing 112, whichcan rotate relative to the head housing 112. Meanwhile, the head housing112 is able to move relative to the spool 111 in a direction parallel tothe axis 110 a.

As shown in FIG. 1D, the spool 111 is provided with a firstcircumferential structure 111 b, and the head housing 112 is providedwith a second circumferential structure 112 d. Under the action of thespring 113, the spool 111 can move upward so that the firstcircumferential structure 111 b is engaged with the secondcircumferential structure 112 d. Thus, the spool 111 can be rotatedsynchronously with the head housing 112. It is noted that, the firstcircumferential structure 111 b and the second circumferential structure112 d have a transmitting surface therebetween which is obliquelyinclined with the axis 110 a.

When the first circumferential structure 111 b and the secondcircumferential structure 112 d are engaged with each other, the usercan start the motor 121 to make the grass trimmer 100 be in a cuttingmode. At this moment, if the trimming line 101 wound on the spool 111 issufficiently long, a part of the trimming line 101 exposed out of thehead housing 112 can cut the vegetation in a whipping action.

Referring to FIGS. 1B-1C, the grass trimmer 100 further includes adamping device 140. Specifically, the damping device 140 includes afriction element 141. The friction element 141 is connected slidablywith the first housing 150 and can move along a direction A. When thefriction element 141 is moved to contact with the head housing 112, thehead housing 112 tends to rotate relative to the spool 111. As thefriction increases, a component force in the direction of the axis 110 ais acted on the head housing 112 due to the inclined transmittingsurface between the first circumferential structure 111 b and the secondcircumferential structure 112 d. The component force can overcome thespring force of the spring 113 sufficiently to make the head housing 112move upward, so that the first circumferential structure 111 b isdisengaged with the second circumferential structure 112 d. Thus, thespool 111 can rotate relative to the head housing 112, and the grasstrimmer 100 is in an auto-winding mode. In the auto-winding mode, thespool 111 driven by the motor 121 can rotate relative to the headhousing 112 under the action of the friction element 141 so as torealize an auto-winding function.

However, when the spool 111 is wound with enough trimming line 101 andthe part of the trimming line 101 exposed out of the head housing is notlong enough to cut the vegetation, the spool 111 can rotate relative tothe head housing 112 so as to feed the trimming line 101 automaticallyfor cutting purposes.

In this embodiment, the function of the friction element 141 is toproduce damping on the head housing 112 so as to slow down the headhousing 112. Thus, the relative rotation is occurred between the headhousing 112 and the spool 111. The user can operate the friction element141 directly or indirectly to switch the grass trimmer 100 between thecutting mode and the auto-winding mode. However, the user can operatethe friction element 141 in a status corresponding to the desired modefirstly, and then start the motor 121.

Referring to FIGS. 2A-2B, a trimming head 210 which is similar to thetrimming head 110 includes a spool 211 and a head housing 212. The spool211 and the head housing 212 are similar to the spool 111 and the headhousing 112 in FIGS. 1-3 . The head housing 212 includes an upper cover212 a and a lower cover 212 b.

A difference between this example and the prior example is that adamping device 240 in FIGS. 2A-2B includes a stop pin 241 for stoppingthe head housing 212 rotating wherein the head housing 212 is formedwith a stop recess 212 c for engaging with the stop pin 241.Specifically, the stop recess 212 c is disposed on the upper cover 212a. In the auto-winding mode, the stop pin 241 is inserted in the stoprecess 212 c so that the head housing 212 is stopped from rotatingrelative the grass trimmer. As the principle described above, therelative rotation between the spool 211 and the head housing 212 canrealize the function of auto-winding.

The function of the stop pin 241 is also to damp the rotation of thehead housing 212. The difference is that, the damping function of thefriction element 141 is to slow down, and the damping function of thestop pin 241 is to limit the movement. Here, slowing down and limitingmovement are both defined as damping. Both the friction element 141 andthe stop pin 241 can be considered as a kind of the damping device.

Referring to FIGS. 3A-3B, a trimming head 310 can be driven to rotateabout an axis 310 a. Specifically, the trimming head 310 includes aspool 311 and a head housing 312. The head housing 312 is formed with anouter aperture 312 a allowing a trimming line to pass through. The spool311 is formed with an inner aperture 311 a.

In this example, a one-way bearing 340 and a supporting element 350 areprovided. The one-way bearing 340 allows two elements or two partsconnected therewith to be able to rotate relatively in one direction,but does not allow them to rotate relatively in another direction. Thesupporting element 350 is connected rotatably with a part of thetrimming head 310 and can support the trimming head 310 rotatably. Thesupporting element 350 may be a first housing for accommodating a motoror a component connected with the first housing fixedly, for example atrimming guard.

More specifically, the one-way bearing 340 is disposed between thesupporting element 350 and the head housing 312, so that the supportingelement 350 is able to rotate unidirectionally relative to the headhousing 312. Taking the supporting element 350 as a reference, the headhousing 312 can rotate in one direction and cannot rotate in anotherdirection.

A driving shaft 322 is connected fixedly with the spool 311, so that thespool 311 can rotate relative to the supporting element 350 in twodirections. Taking the supporting element 350 as a reference, the spool311 can rotate forwardly and reversely.

Similar to the foregoing examples, the spool 311 is provided with afirst circumferential structure 311 a, and the head housing 312 isprovided with a second circumferential structure 312 a which is able toengage with the first circumferential structure 311 a. The difference isthat at least one of the transmitting surfaces of the firstcircumferential structure 311 a and the second circumferential structure312 a is substantially parallel to the axis 310 a. Thus, when the firstcircumferential structure 311 a and the second circumferential structure312 a are rotated in a direction, they cannot disengage with each other.

Based on the arrangement described above, when the motor is rotated in aforward direction, the spool 311 is driven by the driving shaft 322 torotate forwardly. At this moment, the torque is transmitted through thetransmitting surfaces of the first circumferential structure 311 a andthe second circumferential structure 312 a which are substantiallyparallel to the axis 310 a. Meanwhile, the one-way bearing 340 allowsthe head housing 312 to be able to rotate forwardly relative to thesupporting element 350, i.e. the grass trimmer. So, the spool 311 isrotated synchronously with the head housing 312, and the grass trimmerperforms the cutting mode. When the motor is rotated in a reversedirection, the spool 311 is driven by the driving shaft 322 to rotatereversely. The head housing 312 is stopped from rotating reversely bythe one-way bearing 340, so that a relative rotation is created betweenthe spool 311 and the head housing 312. At this moment, the firstcircumferential structure 311 a and the second circumferential structure312 a are disengaged with each other because their contacting surfacesare inclined surfaces. The first circumferential structure 311 a and thesecond circumferential structure 312 a cannot stop the relative rotationbetween the spool 311 and the head housing 312 thoroughly, so therelative rotation is created continuously and the grass trimmer performsthe auto-winding mode.

The function of the one-way bearing 340 is similar to the stop pin 241which is to stop the head housing 312 from rotating. So, the one-waybearing 340 can be considered as a kind of the damping device. Thedifference in the examples is that the friction element 141 and the stoppin 241 are needed to be operated or activated whereas the one-waybearing 340 can realize the damping function in response to a change inthe driving direction of the motor. Thereby, the mechanical structurefor activating the auto-winding mode is simplified. The auto-windingmode and the cutting mode can be switched therebetween by means ofcontrolling the forward and revers rotation of the motor.

In short, the trimming head 310 is driven by the motor around the rotateaxis 310 a, and has the cutting mode, the auto-winding mode, and arelease mode shifted therebeween by use of first and secondcircumferential structures 311 a, 312 a and/or the one-way bearing 340.

Specifically, when the grass trimmer works in the cutting mode, themotor rotates in the first direction, and drives the spool 311 to rotatealong with the head housing 312 by engagement or coupling between thefirst and second circumferential structures 311 a, 312 a.

When the grass trimmer is shifted to be at the release mode, the motorrotates in the first direction to drive the rotation of the trimminghead or spool 311. During the rotation of the trimming head or spool311, the spool 311 and the head housing 312 may be decoupled from eachother to generate a relative rotation therebetween, thereby releasingthe trimming line from the spool 311.

When the grass trimmer is shifted to be at the auto-winding mode, themotor rotates in the second direction opposite to the first direction,and drives the spool 311 to rotate relative to the head housing 312 bythe disengagement of the first and second circumferential structures 311a, 312 a in the opposite second direction. Further, by providing theone-way bearing 340, the head housing or the wire holding member 312 isfixed to the motor case through the damper or one-way bearing device340, and the head housing or the wire holding member 312 cannot berotated, so that the spool 311 and the wire holding member 312 canmaintain a relative rotation relationship therebetween, therebyautomatically winding at least a part of the trimming line around thespool 311, which is being driven by the motor.

In an example auto-winding method for a grass trimmer, with the grasstrimmer including a motor configured for driving a spool, the methodcomprises the steps of:

a) providing a trimming head with the spool included within a headhousing, the head housing having a first housing side and a secondhousing side;

b) inserting a trimming line, through the head housing from a firsthousing side, to enable the trimming line to be coupled to the spool;and

c) driving the spool to rotate relative to the head housing, therebyautomatically winding at least a part of the trimming line around thespool.

Thus, a product of the auto-winding method for a grass trimmer can beachieved.

In a second example, a product of another auto-winding method for agrass trimmer can be also employed to automatically wind at least a partof the trimming line onto or around the spool.

The auto-winding method for the grass trimmer of this example comprisesthe steps of:

a) providing a trimming head with a spool to which a trimmer line can becoupled;

b) providing a motor configured for driving the spool; and

c) activating the motor to drive the spool to enable at least a part ofthe trimming line to be wound around the spool.

Referring to FIGS. 4A-4C, a grass trimmer 400 includes a trimming head410, a driving device 420 and an operating device 430.

The trimming head 410 is configured to mount and accommodate a trimmingline 401. The trimming line 401 is partially accommodated in thetrimming head 410. The trimming line 401 has a part extending out of thetrimming head 410 which is used to cut vegetation when the trimming head410 is rotated.

The trimming head 410 can be driven by the driving device 420 to rotateabout an axis 410 a so as to drive the trimming line 401 to cutvegetation. The operating device 430 is used for the user to operate soas to control the grass trimmer 400.

Specifically, the driving device 420 includes a motor 421 and a drivingshaft 422. The driving shaft 422 is connected fixedly with the trimminghead 410 so as to drive the trimming head 410 to rotate.

The grass trimmer 400 further includes a first housing 450, a secondhousing 460 and a battery pack 470. The first housing 450 is configuredto mount and accommodate the motor 421. The battery pack 470 acting as apower source at least can supply power to the motor 421 of the grasstrimmer 400. The second housing 460 is configured to engage with thebattery pack 470 detachably.

A circuit board is accommodated in the second housing 460, which isconnected with the motor 421 electrically so that the battery pack 470can supply power to the motor 421 and control the motor 421. The firsthousing 450 and the second housing 460 are connected with each otherthrough a connecting rod assembly 490. The operating device 430 isfixedly mounted on the connecting rod assembly 490. The grass trimmer400 further includes an auxiliary handle 491 for the user to grip whichis fixedly mounted on the connecting rod assembly 490.

The trimming line 401 is mounted on the trimming head 410. A guard 480is used to prevent the trimming line 401 from hurting the user, so thatit can realize the function of safety and protection.

Referring to FIGS. 4C-4H, the trimming head 410 includes a spool 411 anda head housing 412.

The spool 411 for winding the trimming line 401 is connected with thedriving shaft 422 and can be driven by the driving shaft 422 to rotateabout the axis 410 a.

The head housing 412 includes an upper cover 412 a and a lower cover 412b. The trimming head 410 further includes a fan 412 c. The fan 412 cincludes blades for generating airflow. The fan 412 c can be driven bythe motor 421 to rotate so as to generate airflow.

In the embodiment in FIGS. 4A-4E, a one-way bearing 440 acting as adamping device is used. The function of the one-way bearing 440 is tomake the head housing 412 connect with the motor 421 in a unidirectionalrotary way. Specifically, a supporting element 452 is connected with themotor 421, which allows the driving shaft 422 to pass through. Thesupporting element 452 is formed with a projecting portion 452 a forsupporting an inner ring of the one-way bearing 440. The one-way bearing440 is not connected with the head housing 412 directly, but connectedbetween the supporting element 452 and the fan 412 c. So, the fan 412 cis only able to rotate unidirectionally relative to the supportingelement 452. Because the fan 412 c is connected with the head housing412 fixedly, the head housing 412 is only able to rotateunidirectionally relative to the supporting element 452 as well.

The upper cover 412 a is formed with first connecting teeth 412 d. Thefan 412 c is formed with second connecting teeth 412 e for engaging withthe first connecting teeth 412 d. Through the engagement between thefirst connecting teeth 412 d and the second connecting teeth 412 e, theupper cover 412 a can be rotated with the fan 412 c synchronously. Theengagement between the first connecting teeth 412 d and the secondconnecting teeth 412 e can provide a guiding effect, so that the headhousing 412 is able to slide relative to the fan 412 c along the axis410 a and the fan 412 c is able to rotate about the axis 410 a togetherwith the head housing 412. That is the fan 412 c is connected with thehead housing 412 fixedly.

The grass trimmer 400 further includes a guard 451 fastened to the firsthousing 450. The guard 451 is able to cover the blades of the fan 412 cin a radial direction of the axis 410 a so as to prevent grass clippingsfrom winding on the fan 412 c. And the guard 451 is able to change thedirection of the airflow of the fan 412 c, so that the airflow generatedby the fan 412 c can blow the grass clippings outward along the radialdirection of the axis 410 a.

The spool 411 is driven directly by the driving shaft 422 to rotate. Thehead housing 412 can rotate relative to the spool 411 a nd sliderelative to the spool 411 in the direction of the axis 410 a.

Referring to FIGS. 4D-4G, the spool 411 is formed with first engagingteeth 411 a on the upper portion and second engaging teeth 411 b on thelower portion. The head housing 412 is formed with first matching teeth412 f and second matching teeth 412 g therein. Specifically, the firstmatching teeth 412 f is formed on the upper cover 412 a, and the secondmatching teeth 412 g is formed on the lower cover 412 b.

When the head housing 412 is at a first axial position relative to thespool 411, the first matching teeth 412 f are engaged with the firstengaging teeth 411 a. So, when the spool 411 is rotated, it can drivethe head housing 412 to rotate synchronously. Specifically, thetransmitting surfaces of the first matching teeth 412 f and the firstengaging teeth 411 a are inclined surfaces, so that the first matchingteeth 412 f and the first engaging teeth 411 a only can rotate togetherunidirectionally. When the spool 411 is rotated reversely, the spool 411rotates relative to the head housing 412 due to the skid between theinclined surfaces.

When the head housing 412 is at a second axial position relative to thespool 411, the second engaging teeth 411 b is engaged with the secondmatching teeth 412 g. Because the transmitting surfaces of the secondengaging teeth 411 b and the second matching teeth 412 g are inclinedsurfaces, the skid can occur between the second engaging teeth 411 b andthe second matching teeth 412 g. So, when the head housing 412 is at thesecond axial position relative to the spool 411, the head housing 412cannot be driven by the spool 411 completely. The head housing 412 stillcan rotate relative to the spool 411, but the speed difference of therelative rotation is decreased by the engagement of the second engagingteeth 411 b and the second matching teeth 412 g.

The trimming head 410 includes a spring 410 b. The spring 410 b cangenerate a force acting between the lower cover 412 b and the spool 411,so that the head housing 412 is biased to the axial position and canrotate with the spool 411 synchronously. That is the first axialposition described above.

The trimming head 410 further includes a first contacting element 410 cand a second contacting element 410 d. The spring 410 b is disposedbetween the first contacting element 410 c and the second contactingelement 410 d and can act on the first contacting element 410 c and thesecond contacting element 410 d directly. The first contacting element410 c and the second contacting element 410 d can prevent the spring 410b from wearing on the spool 411 and the head housing 412, which are madeof metal.

The trimming head 410 further includes a button 410 e which is connectedrotatably with the lower cover 412 b. A bearing 410 f is disposedbetween the button 410 e and the lower cover 412 b, so that the button410 e can be rotated relative to the lower cover 412 b. Meanwhile, thebutton 410 e and the lower cover 412 b can move together in thedirection of the axis 410 a. When the position of the button 410 e ischanged, the lower cover 412 b can move therewith. That is, the axialposition of the head housing 412 can be changed when the button 410 e isbumped.

When the grass trimmer 400 is in the cutting mode, the user can bump thetrimming head 410, and the button 410 e contacts with the ground to makethe head housing 412 slide, so that the first engaging teeth 411 a isdisengaged with the first matching teeth 410 f and rotated relative tothe first matching teeth 410 f. Further, when the button 410 e isbumped, the head housing 412 can slide to the second axial positionrelative the spool 411 and rotate at a lower speed relative to the spool411. So, the trimmer line 401 wound on the spool 411 can be fed out ofthe head housing 412 partially, and the grass trimmer 400 performs aline feeding mode. This arrangement has advantages that is, when themotor 421 is rotated at a speed in the cutting mode, the relativerotation speed of the head housing 412 and the spool 411 is controlled,so that the trimmer line 401 cannot be fed excessively during eachbumping.

The button 410 e is able to rotate freely relative to the lower cover412 b under the action of the bearing 410 f, so that the wearing of thetrimmer head 410 is reduced. The spring 410 b can generate a forceacting on the head housing 412 so as to make the head housing 412 movedownwardly relative to the spool 411. An anti-vibration element 410 g isdisposed between the upper cover 412 e and the spool 411 for reducingthe impact between the upper cover 412 e and the spool 411.Specifically, the anti-vibration element 410 g is a rubber washer.

The spool 411 is formed with an inner aperture 411 c and the headhousing 412 is formed with an outer aperture 412 h allowing the trimmingline 401 to pass from the inside to the outside of the head housing 412.When the cutting mode is finished, the inner aperture 411 c and theouter aperture 412 h are aligned automatically in the circumferentialdirection. Or, when the trimming line 40 a is not mounted on thetrimming head 410 and the motor 421 is stopped, the inner aperture 411 cand the outer aperture 412 h are aligned automatically in thecircumferential direction.

The spool 411 is formed with several inner apertures 411 c, and thenumber of the inner apertures 411 c is even. The several inner apertures411 c are distributed uniformly in the circumferential direction of theaxis 410 e. Specifically, the number of the first engaging teeth 411 ais corresponded with the number of the inner apertures 411 c. Similarly,the number of the second engaging teeth 411 b is corresponded with thenumber of the inner apertures 411 c. The spool 411 is formed with sixinner apertures 411 c. The spool 411 is further formed with six firstengaging teeth 411 a and six second engaging teeth 411 b.

The spool 411 is formed with a guiding opening 411 d for guiding thetrimming line 401 to enter the inner apertures 411 c. The guidingopening 411 d is expanded gradually along the radial direction of therotating axis of the spool 411. The first engaging teeth 411 a areformed with inclined surfaces.

The guiding opening 411 d has a maximum size L1 in the circumferentialdirection of the axis 410 a which is greater than a maximum size L2between two adjacent first engaging teeth 411 a in the circumferentialdirection of the axis 410 a.

When the grass trimmer 400 is in the cutting mode, the transmittingsurfaces of the first engaging teeth 411 a and the first matching teeth412 f are so arranged that the outer apertures 412 h and the innerapertures 411 c can be aligned automatically in the circumferentialdirection when the motor 421 is stopped. Here, the word “align” meansthat the trimming line 401 passing through the outer apertures 412 h canbe guided into the inner apertures 411 c directly.

The spool 411 is formed with a first flange 411 e and a second flange411 f on its two ends. The spool 411 is further formed with a divisionplate 411 g in the middle portion. A first winding portion for windingand accommodating the trimmer line 401 is formed between the firstflange 411 e and the division plate 411 g. A second winding portion forwinding and accommodating the trimmer line 401 is formed between thesecond flange 411 f and the division plate 411 g.

In the cutting mode, the spool 411 is driven by the driving shaft 422 torotate, and the upper cover 412 a is driven by the spool 411 to rotate.The fan 412 c is driven by the upper cover 412 a to rotate. The fan 412c can rotate relative to the second housing 460 in a first directionreferring to an arrow B in FIG. 4 b . At this moment, the motor 421 isrotated forwardly so as to drive the spool 411 and the head housing 412to rotate in the first direction.

As shown in FIG. 4 h , when it is needed to supplement the trimming line401, two ends of the trimming line 401 can be passed through theopposite outer apertures 412 h of the head housing 412 respectively, andthen the two ends of the trimming line 401 are extended into the twoopposite inner apertures 411 c of the spool 411 respectively. Sure, theuser can insert two trimming lines 401 into the two inner apertures 411c respectively. At this moment, the user can control the grass trimmer400 to make it perform the auto-winding mode. The motor 421 is rotatedreversely so as to drive the spool 411 to rotate in a second directionopposite to the first direction. Due to the effect of the one-waybearing 440, the fan 412 c cannot rotate in the second direction. Thefan 412 c is connected with the head housing 412 through the firstconnecting teeth 412 d and the second connecting teeth 412 e, so thehead housing 412 cannot rotate in the second direction. The spool 411 isdriven by the driving shaft 422 to rotate relative to the head housing412 in the second direction so as to realize the auto-winding function.

Otherwise, the first engaging teeth 411 a, the second engaging teeth 411b, the first matching teeth 410 f and the second matching teeth 410 gare inclined teeth. The inclined surfaces of the inclined teeth cannotstop the spool 411 rotating relative to the head housing 412.

When the spool 411 is wound with enough trimming line 401, the excesstrimming line 401 which has not been wound needs to be to cut off.Referring to FIGS. 4A and 4H, the grass trimmer 400 includes a linebreaking device 481 for cutting off the trimming line 401 automaticallyin the auto-winding mode.

The line breaking device 481 includes a line breaking element 482. Thetrimming head 410 can rotate relative to the line breaking element 482.The line breaking element 482 is fastened to the guard 480. In theauto-winding mode, the trimming line 401 can be driven by the trimminghead 410 to pass the line breaking element 482. When the trimming line401 is tensioned, it can be cut off by the line breaking element 482. Inthe cutting mode and feeding mode, the trimming line 401 can be cut offin the middle by the line breaking element 482, and the trimming line401 is divided into two parts.

Sure, the trimming line 401 can be cut off in a bumping way when it istensioned on the outside of the head housing 412.

Referring to FIGS. 4I and 4J, the operating device 430 includes a firstoperating element 431 and a second operating element 432. The firstoperating element 431 has an initial status and a first preset operatingstatus. The second operating element 432 has an initial status and asecond preset operating status. As shown in FIG. 4I, the first operatingelement 431 and the second operating element 432 are in the initialstatus. As shown in FIG. 4J, the first operating element 431 is in thefirst preset operating status and the second operating element 432 is inthe second preset operating status. When the first operating element 431and the second operating element 432 are in the first preset operatingstatus and the second preset operating status respectively, the grasstrimmer 100 can start the auto-winding mode.

The operating device 430 includes a first resetting assembly 433 and asecond resetting assembly 434. The first resetting assembly 433 can makethe first operating element 431 get out of the first preset operatingstatus when the first operating element 431 is not operated by the user.The second resetting assembly 434 can make the second operating element432 get out of the second preset operating status when the secondoperating element 432 is not operated by the user.

When the user only operates the first operating element 431 and does notoperate the second operating element 432, that is the second operatingelement 432 is not in the second preset operating status, the firstoperating element 431 is operated to move to the first preset operatingstatus. At this moment, the grass trimmer 400 is in the cutting mode.

Referring to FIGS. 4K and 4L, another operating device 730 includes afirst operating element 731 and a second operating element 732. Thefirst operating element 731 is used to activate a motor. The secondoperating element 732 is used for the user to operate so as to choosethe auto-winding mode of the grass trimmer. The second operating element732 has a first position a second position. As shown in FIG. 4K, thesecond operating element 732 is in the first position which correspondswith the auto-winding mode. At this moment, when the motor is activatedby the first operating element 731, the grass trimmer goes into theauto-winding mode. As shown in FIG. 4L, the second operating element 732is in the second position which corresponds with the cutting mode. Atthis moment, when the motor is activated by the first operating element731, the grass trimmer goes into the cutting mode.

As shown in FIG. 4M, in another alternative embodiment, a line breakingdevice 781 can cut off a trimming line 701 in the auto-winding mode. Theline breaking device 781 includes a line breaking element 782 which isable to rotate with a trimming head 710 synchronously. In theauto-winding mode, the trimming line 701 is driven by the trimming head710 to close to the line breaking element 782 so that the trimming line701 is cut off. The line breaking element 782 is fixed to a head housing712. In the auto-winding mode, the trimming line 701 is close to thehead housing 712. When the trimming line 701 is tensioned and contactswith the line breaking element 782, it is cut off by the line breakingelement 782.

In the embodiment in FIG. 4A, the head housing 412 is formed with outerapertures 412 h. In the auto-winding mode, the head housing 412 isrotated relative to the spool 411. The head housing 412 acts as a handof the user winding the trimming line 401, and the outer apertures 412 hact as the fingers of the user holding the trimming line 401. So, thehead housing 412 can be defined as a line holding element. The lineholding element can hold the trimming line 401 so that the trimming line401 can rotate relative to the spool 411. The outer apertures 412 h canbe defined as a line holding structure. The line holding structure actsas the fingers to hold and locate the trimming line 401, and meanwhileallow the trimming line 401 to pass the outer apertures 412 hcontinuously and wind on the spool 411.

Referring to FIGS. 5A-5C, a grass trimmer 500 includes a trimming head510, a driving device 520 and an operating device 530.

The driving device 520 includes a driving shaft 522. The driving shaft522 is connected with the trimming head 510 so as to drive the trimminghead 510 to rotate about a central axis 502. The driving device 520further includes a motor 521. Specifically, the driving shaft 522 is anoutput shaft of the motor 521.

The grass trimmer includes a first housing 550, a second housing 560 anda battery pack 570. The motor 521 is fixed to the first housing 550. Thebattery pack 570 for supplying power to the motor 521 is connected withthe second housing 560 detachably. Further, a circuit board is disposedin the second housing 560, which is connected with the motor 521 tocontrol the motor 521. The first housing 550 and the second housing 560is connected through a connecting rod assembly 590. The operating device530 is fixed to the connecting rod assembly 590. The grass trimmer 500further includes an auxiliary handle 591 fixed to the connecting rodassembly 590 for the user to grip.

A trimming line 501 is mounted on the trimming head 510. A guard 580 canprevent the trimming line 501 from hurting the user so as to realize thefunction of protection.

Referring to FIGS. 5D-5G, the trimming head 510 includes a spool 511 anda head housing 512. The spool 511 allowing the trimming line 501 to windthereon is formed with an inner aperture 511 a and the end of thetrimming line 501 is extended into the inner aperture 511 a.Specifically, the spool 511 is formed with two inner apertures 511 a onthe opposite sides. Two trimming lines 501 can be inserted in the twoinner apertures 511 a respectively. Or, two ends of one trimming line501 can be inserted in the two inner apertures 511 a respectively. Thespool 511 is accommodated in the head housing 512. The head housing 512includes an upper cover 512 a and a lower cover 512 b which are coupledwith each other through a snap joint.

The spool 511 is disposed between the upper cover 512 a and the lowercover 512 b. The head housing 512 is formed with outer apertures 512 callowing the trimming line 501 to go through the head housing 512 fromthe inside. Specifically, the outer apertures 512 c are formed on thelower cover 512 b. Further, the trimming head 510 includes eyelets 518fastened on the lower cover 512 b which allow the trimming line 501 topass through. More specifically, the eyelets 518 are made of metal whichcan prevent the trimming line 501 from wearing the lower cover 512 b.

The grass trimmer 500 further includes a one-way bearing 513. When theone-way bearing 513 is rotated in one direction, an inner ring and anouter ring of the one-way bearing 513 are rotated synchronously. While,when the one-way bearing 513 is rotated in the reverse direction, theinner ring is rotated relative to the outer ring. When the driving shaft522 is rotated in one direction, the one-way bearing 513 allows the headhousing 512 and the spool 511 to rotate synchronously. While, when thedriving shaft 522 is rotated in the reverse direction, the spool 511 isrotated relative the head housing 512 under the action of the one-waybearing 513.

The trimming head 510 includes an elastic element 514 which is able togenerate a force between the head housing 512 and the spool 511. Theforce acts on the head housing 512 to make the head housing 512 departfrom the first housing 550 or the motor 521. Specifically, elasticelement 514 is disposed between the lower cover 512 b and the spool 511.The spool 511 can apply force on the lower cover 512 b and the spool 511respectively through its two ends. The two ends can be connected withthe lower cover 512 b and the spool 511 directly and apply force onthem, or connected with the lower cover 512 b and the spool 511indirectly and apply force on them through other components.

Specifically, the trimming head 510 further includes a washer 514 adisposed between the elastic element 514 and the spool 511. The force ofthe elastic element 514 is transferred to the spool 511 through thewasher 514 a. When the spool 511 is rotated relative to the head housing512, the elastic element 514 is rotated relative to the spool 511. Thewasher 514 a is able to prevent the elastic element 514 from wearing thespool 511. When the trimming head 510 is bumped by the user, the elasticelement 514 is compressed, and the head housing 512 is moved in adirection close to the first housing 550 or the motor 521. As shown inFIG. 5B, the head housing 512 is moved upward. When the bumping isfinished, the elastic element 514 can apply force on the lower cover 512b so as to make the lower cover 512 b to move downward or in thedirection far from the first housing 550 or the motor 521. So, the linebump feeding is realized.

The grass trimmer 500 further includes a fan 515. The fan 515 can beformed by the head housing 512 or a separate element. Specifically, thefan 515 is a separate element, which is connected with the driving shaft522 and driven by the driving shaft 522 to rotate. Alternatively, thefan can be connected with the head housing and driven by the headhousing to rotate.

Specifically, the fan 515 is provided with several blades 515 a. Thetrimming head 510 includes an end cap 515 b fixed to the fan 515. Morespecifically, the end cap 515 b is fixed to the blades 515 a. The endcap 515 b has an annular shape and allows the driving shaft 522 to passthrough. The fan 515 is disposed between the motor 521 and the headhousing 512. The fan 515 is also disposed between the first housing 550and the head housing 512. The fan 515 is also disposed between the firsthousing 550 and the spool 511. The upper cover 512 a is disposed betweenthe fan 515 and the lower cover 512 b. The upper cover 512 a is alsodisposed between the fan 515 and the spool 511. It can be considered asthe fan 515 is disposed above the head housing 512.

The spool 511 is connected with the driving shaft 522 so as to rotatewith the driving shaft 522 synchronously. The fan 515 is rotated withthe driving shaft 522 and the spool 511 synchronously. The spool 511 isfixed to the driving shaft 522 through a locating nut 522 a, so theaxial position of the spool 511 relative to the driving shaft 522 islimited.

The trimming head 510 further includes a connecting element 516 which isformed with a plurality of feeding teeth 516 a for feeding line. Thehead housing 512 is formed with a plurality of matching teeth 512 d forengaging with the feeding teeth 516 a. The matching teeth 512 d isengaged with the feeding teeth 516 a so as to control the line bumpfeeding.

The trimming head 510 further includes a connecting shaft 513 a fixed tothe driving shaft 522. The fan 515 is fixed to the connecting shaft 513a, so that the fan 515 can be driven by the driving shaft 522 to rotate.The one-way bearing 513 is fixed to the connecting shaft 513 a.Specifically, the connecting shaft 513 a is disposed in the inner ringof the one-way bearing 513. So, the driving shaft 522 can drive theinner ring of the one-way bearing 513 to rotate, and the inner ring isrotated with the driving shaft 522 synchronously. Further, theconnecting shaft 513 a can limit the axial position of the one-waybearing 513 relative to the driving shaft 522. The connecting element516 is fixed to the outer ring of the one-way bearing 513 and rotatedwith the outer ring synchronously. The one-way bearing 513 and theconnecting element 516 are fixed by a screw 513 b, so the displacementof the one-way bearing 513 and the connecting element 516 in the axialdirection is limited. The connecting element 516 is engaged with thehead housing 512 through the engagement of the feeding teeth 516 a andthe matching teeth 512 d. The head housing 512 is driven to rotate bythe connecting element 516.

Referring to FIGS. 5D-5L, the trimming head 510 further includeslocating elements 517 for aligning the inner apertures 511 a and theouter apertures 512 c. When it is needed to add a new trimming line 501to the spool 511, the user can make the head housing 512 rotate to alignwith the spool 511 conveniently. The trimming line 501 is passed throughthe outer apertures 512 c of the head housing 512 and entered into theinner apertures 511 a. The locating elements 517 are fixed to the spool511. The trimming head 510 includes a pressing plate 517 a for fixingthe locating elements 517 to the spool 511. The lower cover 512 b isformed with locating recesses 512 e for engaging with the locatingelements 517. When the locating elements 517 are entered into thelocating recesses 512 e partially, the inner apertures 511 a and theouter apertures 512 c are aligned.

Referring to FIGS. 5F and 5G, the trimming head 510 is in a free statewhich is not bumped. Referring to FIGS. 5J and 5K, the trimming head 510is in a compressed state which is bumped. When the user bumps thetrimming head 510 to feed the trimming line 501, the lower cover 512 bis contacted with the ground, and the ground applies an upward force tothe lower cover 512 b so that the upper cover 512 a and the lower cover512 b move upward to the state in FIGS. 5J and 5K relative to the spool511, the fan 515, the motor 521 and the driving shaft 522. At thismoment, the head housing 512 is rotated to a certain angle relative tothe spool 511. The angle is limited by the engagement of the feedingteeth 516 a and the match teeth 512 d, so a specific length of thetrimming line 501 is released. When the user raises the trimming head510, the force acting on the lower cover 512 b by the ground disappears.The elastic element 514 generates a force to make the lower cover 512 bmove downward or in a direction far from the spool 511 to the state inFIGS. 5F and 5G. The line bump feeding is finished. This feeding mode iscalled bump feeding mode. The feeding mode means that an end of thetrimming line 501 is disengaged from the spool 511 and extended out ofthe head housing 512. Or, it could be said that the length of thetrimming line 501 located out of the head housing 512 is increased. Or,it could be said that the length of the trimming line 501 for cuttingvegetation is increased.

As shown in FIG. 5B, when the grass trimmer is in the cutting mode, thetrimming head 510 is rotated clockwise in a direction indicated by anarrow. The spool 511 and the head housing 512 are all rotated clockwise.In the cutting mode, the trimming line 501 is fixed relative to thetrimming head 510. The spool 511 is fixed relative to the head housing512. The grass trimmer 500 also has the auto-winding mode. In theauto-winding mode, the spool 511 is rotated relative to the head housing512, and the trimming line 501 located out of the head housing 512 iswound on the spool 511 gradually. The rotation direction of the spool511 in the auto-winding mode is opposite to the rotation direction ofthe spool 511 in the cutting mode. In the auto-winding mode, the headhousing 512 is fixed. Specifically, the head housing 512 is stopped fromrotating in the same direction as the spool 511. That is the headhousing 512 is stopped from rotating counterclockwise.

Refereeing to FIGS. 5L to 5Q, the grass trimmer 500 further includes adamping device 540 which is fixed by the first housing 550. The dampingdevice 540 includes a stopping element 541 which is a damping element.The stopping element 541 is used to stop the head housing 512 rotatingin one direction relative to the first housing 550. The damping device540 further includes an activating element 542 and a reset spring 543.The stopping element 541 is controlled to be at different positions bythe activating element 542. The reset spring 543 can generate forceacting on the stopping element 541 so as to make the stopping element541 restore to an initial state. The grass trimmer 500 further includesa guard 551 fixed on the first housing 550.

The reset spring 543 is connected with the stopping element 541 and theguard 551 on its two ends respectively and can apply force between thestopping element 541 and the guard 551. The damping device 540 includesa protecting element 544 and a guiding element 545. The activatingelement 542 is covered by the protecting element 544 so that the user iseasy to operate the activating element 542. The guiding element 545 isengaged with the stopping element 541 and the activating element 542 soas to guide the stopping element 541 and the activating element 542. Theguiding element 545 is fixed on the first housing 550, which can beintegrated with the guard 551 or the first housing 550. The guard 551can be integrated with the first housing 550. The guard 551, the firsthousing 550 and the guiding element 545 can be integrated as acomponent.

The head housing 512 is provided with stopping bulges 512 f The stoppingbulges 512 f can be engaged with the stopping element 541 for stoppingthe head housing 512 from rotating relative to the spool 511.Specifically, the stopping bulges 512 f are formed on the upper cover512 a and located on the edge of the upper cover 512 a.

The stopping element 541 has a first position and a second positionrelative to the trimming head 510 or the first housing 550. Referring toFIGS.5B and 5N, in the first position, that is the initial position ofthe stopping element 541, the stopping element 541 is separated from thehead housing 512 and disengaged with the stopping bulges 512 f to stopthe head housing 512 from rotating in one direction. Or, it could besaid that the stopping element 541 is not extended downward. Referringto FIGS. 5L and 5Q, in the second position, that is a stopping position,the stopping element 541 is contacted with the head housing 512 so as tostop the head housing 512 from rotating in one direction relative to thefirst housing 550. Specifically, the engagement of the stopping element541 and the stopping bulges 512 f can stop the head housing 512 fromrotating counterclockwise as the arrow shown in FIG. 5L.

The stopping element 541 is able to slide relative to the trimming head510 or the first housing 550. The stopping element 541 is able to slidein the direction of the rotating axis of the trimming head 510. Or, itcould be said that the sliding direction of the stopping element 541 issubstantially parallel to the rotating axis of the trimming head 510.The stopping element 541 is able to rotate relative to the first housing550 about a rotating axis. The rotating axis of the stopping element 541is substantially parallel to the rotating axis of the trimming head 510or the driving shaft 522.

Specifically, the stopping element 541 is provided with guiding ribs 541a. The guiding element 545 is formed with guiding slots 545 a. When thestopping element 541 slides relative to the first housing 550, theguiding ribs 541 a slide in the guiding slots 545 a. The engagement ofthe guiding ribs 541 a and the guiding slots 545 a can stop the stoppingelement 541 from rotating relative to the first housing 550. Theactivating element 542 is provided with limiting ribs 542 a. Theengagement of the limiting ribs 542 a and the guiding slots 545 a canstop the activating element 542 from rotating relative to the firsthousing 550. The activating element 542 is formed with a driving surface542 b. The stopping element 541 is formed with an engaging surface 541b. Specifically, the driving surface 542 b is formed on the bottom ofthe activating element 542, and the engaging surface 541 b is formed onthe top of the guiding ribs 541 a. When the activating element 542 ispressed downward, the stopping element 541 is pressed to move downwardby the activating element 542. The guiding ribs 541 a of the stoppingelement 541 slide in the guiding slots 545 a and disengage from theguiding slots 545 a finally, and the limiting ribs 542 a of theactivating element 542 are still in the guiding slots 545 a. So, theactivating element 542 is stopped from rotating relative to the firsthousing 550. At this moment, the driving surface 542 b is engaged withthe engaging surface 541 b so as to constitute an engagement of inclinedsurfaces. Thus, the stopping element 541 is rotated relative to theactivating element 542 or the first housing 550 and reaches the stoppingposition finally.

When the auto-winding mode is finished, the user can control thetrimming head 510 to enter the cutting mode or the feeding mode, and thetrimming head 510 is rotated in another direction. Specifically, therotation direction of the motor in the cutting mode is different fromthe rotation direction of the motor in the auto-winding mode. And therotation direction of the motor in the feeding mode is different fromthe rotation direction of the motor in the auto-winding mode. When theauto-winding mode is finished and going into the cutting mode or thefeeding mode, the trimming head 510 is driven to rotate reversely by themotor. At this moment, the head housing 512 is rotated clockwise in adirection indicated by the arrow in FIG. 19 . This direction is oppositeto the rotation direction of the head housing 512 stopped by thestopping element 541. The stopping bulges 512 f on the head housing 512is contacted with the stopping element 541 so as to drive the stoppingelement 541 to rotate. When the guiding ribs 541 a of the stoppingelement 541 is rotated to align with the guiding slots 545 a, thestopping element 541 is moved upward under the action of the resetspring 543. The guiding ribs 541 a slide upward in the guiding slots 545a and restore to the initial position.

As shown in FIG. 5A, the operating device 530 includes a first operatingelement 531 and a second operating element 533. When the first operatingelement 531 is triggered, the grass trimmer 500 is in the cutting mode.The second operating element 533 is used for the user to start theauto-winding mode of the grass trimmer 500. The operating device 530further includes a handle housing 532 for the user to grip. The firstoperating element 531 and the second operating element 533 are connectedwith the handle housing 532. The first operating element 531 and thesecond operating element 533 are close to each other for easy operationby the user.

Specifically, the grass trimmer 500 includes a first electronic switchand a second electronic switch. The first electronic switch iscontrolled by the first operating element 531, and the second electronicswitch is controlled by the second operating element 533. When the firstoperating element 531 is triggered, the second operating element 533cannot be triggered. Similarly, when the second operating element 533 istriggered, the first operating element 531 cannot be triggered. When thefirst operating element 531 is triggered, the grass trimmer 500 is inthe cutting mode. And when the second operating element 533 is triggeredwhile the first operating element 531 is not released, the grass trimmer500 cannot go into the auto-winding mode. Similarly, when the secondoperating element 533 is triggered, the grass trimmer 500 is in theauto-winding mode. And when the first operating element 531 is triggeredwhile the second operating element 533 is not released, the grasstrimmer 500 cannot go into the feeding mode. Alternatively, the grasstrimmer includes a first electronic switch which can be controlled bythe first operating element and the second operating element.

The first operating element 531 is able to start the motor 521. When themotor 521 is started by the first operating element 531, the motor 521rotates in a first running state.

The second operating element 533 is able to start the motor 521. Whenthe motor 521 is started by the second operating element 533, the motor521 rotates in a second running state. The rotation direction of themotor 521 in the first running state is different from the rotationdirection of the motor 521 in the second running state. In theauto-winding mode, the motor 521 runs in the second running state. Inthe cutting mode, the motor 521 runs in the first running state, and therotational speed of the motor 521 is greater than or equal to 4000 rpmand less than or equal to 8000 rpm.

Specifically, when the grass trimmer 500 is in the auto-winding mode,the rotational speed of the spool 511 is greater than or equal to 100rpm and less than or equal to 2000 rpm. More specifically, therotational speed of the spool 511 is greater than or equal to 300 rpmand less than or equal to 800 rpm. Alternatively, the rotational speedof the spool 511 is greater than or equal to 30 rpm and less than orequal to 600 rpm. Or, the rotational speed of the spool 511 is greaterthan or equal to 60 rpm and less than or equal to 300 rpm. A ratio ofthe rotational speeds of the spool 511 in the cutting mode and in theauto-winding mode is greater than or equal to 5 and less than or equalto 300. Further, the ratio of the rotational speeds of the spool 511 inthe cutting mode and in the auto-winding mode is greater than or equalto 10 and less than or equal to 200.

As shown in FIG. 6A, a motor 621 has a driving shaft 622 for driving ahead housing 612 and a one-way bearing 640 and a damping device 611 areprovided.

A driving device 620 includes the motor 621. A trimming head 610includes a spool 611 and the head housing 612.

A supporting element 650 is configured as a housing for accommodatingthe motor 621. The one-way bearing 640 is disposed between the spool 611and the supporting element 650, so that the spool 511 can only rotateunidirectionally relative to the supporting element 650.

The driving shaft 622 passes through the spool 611, but the spool 611 isnot driven by the driving shaft 622 directly. That is, the torque is nottransmitted directly between the driving shaft 622 and the spool 611.The driving shaft 622 is connected fixedly with the head housing 612,and the head housing 612 is driven by the head housing 612 directly. Andthen the spool 611 is driven by the head housing 612 through thetransmission structure in FIG. 3B.

According to the example and the principle described above, when themotor 621 is rotated forwardly, the spool 611 and the head housing 612can be rotated synchronously so as to perform the cutting mode. When themotor 621 is rotated reversely, the spool 611 is rotated relative to thehead housing 612 so as to perform the auto-winding mode.

It can be understood that the damping device can not only apply aresistance force on the head housing to damp its rotation, but can alsoapply a resistance force on the spool to damp its rotation.

In another example, the damping device can apply a resistance force bothon the head housing and on the spool. For example, more than one dampingelement can be disposed based on the embodiment in FIG. 6A, so that thehead housing 612 can be damped and slowed down through contacting in theauto-winding mode.

In other words, the damping device includes a first damping element anda second damping element. The first damping element can apply a firstresistance force on the spool to damp its rotation. The second dampingelement can apply a second resistance force on the head housing to dampits rotation. Thus, the head housing can be rotated relative to thespool under the effect of the first resistance force and the secondresistance force.

Referring to FIGS. 7A-7B, a trimming head 810 includes a spool 811 and ahead housing 812 which are similar to the spool and the head housingdescribed previously. A driving shaft 822 is connected directly with thespool 811 so as to drive the spool 811 to rotate. The spool 811 and thehead housing 812 are formed with transmission structures 811 a and 812 arespectively which can be engaged with each other. When the head housing812 is at an axial position as shown in FIG. 7A, the transmissionstructures 811 a and 812 a are engaged with each other, so the headhousing 812 is driven by the spool 811 to rotate together. While, whenthe head housing 812 is at an axial position as shown in FIG. 7B, thetransmission structures 811 a and 812 a are disengaged from each other.At this moment, if the head housing 812 is damped, the spool 811 isrotated relative to the head housing 812.

For controlling the axial position of the head housing 812, anelectromagnet 813 is provided, and a magnetic element 812 b is fastenedon the head housing 812. A supporting element 814 can be provided formounting the electromagnet 813. The supporting element 814 can be aguard of the grass trimmer, a housing of the motor or other partsconnected fixedly with them.

When it is needed to perform the auto-winding mode, the electromagnet813 is powered on to generate a magnetic field so as to attract themagnetic element 812 b. So, the axial position of the head housing 812is changed. At this moment, the motor is controlled so as to make thedriving shaft 822 drive the spool 811, and a relative rotation iscreated between the spool 811 and the head housing 812. While, when itis needed to perform the cutting mode, the electromagnet 813 does notgenerate the magnetic field, and the head housing 812 is moved in theaxial direction so as to make the transmission structures 811 a and 812a engage. Thus, the spool 811 and the head housing 812 are rotatedsynchronously.

Alternatively, the magnetic element 812 b is an annular element. Theelectromagnet 813 is disposed at a corresponding position. However, apart of the head housing 812 can be made of magnetic material or metalmaterial.

Referring to FIGS. 8A-8B, a trimming head 810′ includes a rope, wire,cable, or the like 813′. The rope 813′ passes through a driving shaft822′ directly, which is used to pull a head housing 812′ to change theposition of the head housing 812′. Thus, a spool 811′ can be rotatedrelative to the head housing 812′.

Referring to FIGS. 8C-8D, a trimming head 810″ includes a rope 813″ forpulling a head housing 812″ from the top so as to change the position ofthe head housing 812″. Thus, a spool 811″ can be rotated relative to thehead housing 812″. Surely, the motor can be used to drive the headhousing or the similar method can be used to change its position so asto realize the function above.

In the embodiments as shown in FIG. 7A-8D, a clutch device is providedfor disengaging the spool and the head housing when it is needed. So,only one of the spool and the head housing is driven by the drivingshaft, and the relative rotation is created between them. While, whenthe spool and the head housing are needed to rotate synchronously, theyare engaged, so that one of them can drive the other.

As shown in FIG. 9A, a grass trimmer 900 includes a brushless motor 901,a driving circuit 902, a controller 903, a detecting device 904, a powersupply circuit 905 and a power supply 906.

The brushless motor 901 includes three-phase windings with Y-typeconnection. Surely, the three-phase windings can use triangularconnection.

The driving circuit 902 is used to drive the brushless motor 901. Asshown in FIG. 9B, specifically, the driving circuit 902 includes sixsemiconductor switches Q1-Q6 which constitute a full-bridge circuit withsix arms. The terminals of the windings of the brushless motor 901 areconnected between two corresponding semiconductor switches of thedriving circuit 902. The semiconductor switches Q1- Q6 can be driven bycorresponding electrical signals so as to conduct the circuit at acertain duty cycle. Thus, the current passes the corresponding windingto drive the brushless motor 901. It is noted that the controllingsignal can control the current of the brushless motor 901 throughcontrolling the duty cycle of the semiconductor switches Q1-Q6 so as tocontrol the speed of the brushless motor 901.

The controller 903 is used to control the driving circuit 902, and inparticular to send controlling signals to the driving circuit 902. Thecontroller 903 can be constituted by a main chip mainly for operatingand outputting signals and a driving chip mainly for sending drivingsignals to the driving circuit 902. The main chip controls the drivingcircuit 902 through controlling the driving chip. Surely, the controller903 can be constituted by one chip.

The detecting device 904 includes a Hall sensor which including severalHall elements. The detecting device 904 can determine the speed of arotor of the brushless motor 901 according to the signal change of theHall elements.

The detecting device 904 can detect the voltage and current of thewindings of the brushless motor 901 and feedback to the controller 903as the control basis of the controller 903.

The power supply circuit 905 is mainly used to adjust the voltage of thepower supply 906 so that the controller 903 can obtain proper powersupply. The power supply 906 is mainly used to supply power to the grasstrimmer 900. Alternatively, the power supply 906 is a battery devicewhich can be charged repeatedly.

In this example, a physical switch 907 can be disposed between thecontroller 903 and the power supply circuit 905 which can be controlledby the user to switch on or off the electric connection between thecontroller 903 and the power supply circuit 905, so the controller 903cannot drive the brushless motor 901.

The physical switch 907 can be acted as a main switch of the grasstrimmer 900, which is used for the user to control the start of thebrushless motor 901.

As shown in FIG. 9A, a signal switch 908 can be provided. The signalswitch 908 is able to be operated by the user to send different signals.The controller 903 can output different control modes according to thesignals sent by the signal switch 908, so that the brushless motor 901has different running states. Thus, the signal switch 908 can be actedas an operating element for the user to choose the cutting mode or theauto-winding mode.

Specifically, when the user chooses the cutting mode, the signal switch908 sends a first signal. At this moment, the user controls the physicalswitch 907 to power on the controller 903. The controller 903 enters afirst control mode according to the first signal received and outputsthe driving signal to the driving circuit 902 so as to make thebrushless motor 901 rotate forwardly at a high speed. When the userchooses the auto-winding mode, the signal switch 908 sends a secondsignal which is different from the first signal. The controller 903enters a second control mode according to the second signal and outputsthe control signal so as to make the brushless motor 901 rotatereversely at a low speed.

Surely, two physical switches or two signal switches can be used, whichcan be used to switch the modes and control the start of the brushlessmotor 901 respectively.

The speed can be controlled by the duty cycle used for driving thedriving circuit 902 when the controller 903 is in the first control modeand the second control mode. The controller 903 can output the drivingsignal at a high duty cycle in the first control mode, and output thedriving signal at a low duty cycle in the second control mode.

Otherwise, in order to make the winding stop automatically, the currentof the brushless motor 901 can be detected by the detecting device 904.As shown in FIG. 4H, when the winding is finished, the trimming line istensioned, and the current of the brushless motor 901 is increasedsuddenly. The controller 903 can determine whether the trimming line istensioned according to a current threshold or a current slop thresholdso as to make the brushless motor 901 in the auto-winding mode stop.

Otherwise, as the trimming line is being wound, the load of thebrushless motor 901 becomes high due to the increase of the mass of thetrimming line. So, the current of the brushless motor 901 increases.Thus, a current threshold can be set to determine whether the winding isfinished. Similarly, the speed of the motor decreases due to theincrease of the load. Thus, a speed threshold or a speed slop thresholdcan be set to determine whether the winding is finished. When the speeddecreases fast or decreases to a certain extent, the controller 903determines that the auto-winding is finished.

Or, a position sensor or an optical sensor can be used to determine theposition and state of the trimming line so as to finish the auto-windingmode.

Otherwise, based on the same principle, in order to prevent the userfrom starting the auto-winding mode accidentally while the trimming headstill has trimming line stored therein, the controller 903 activates theauto-winding mode firstly. If a representation of the high load occurs,for example the large current or low speed, the controller 903 candetermine that the auto-winding mode is not suitable for running at thismoment. And then the brushless motor 901 is stopped to drive, and asound signal or a light signal can be used to remind the user.

In a word, the controller 903 can determine the load state of thebrushless motor 901 according to the speed or current of the brushlessmotor 901 so as to determine when to stop the winding and whether theauto-winding mode is suitable currently.

Specifically, the controller 903 can realize the controlling method asfollowing:

a) starting the auto-winding mode;

b) determining whether the winding is suitable currently, if yes, thengoing to the next step, if no, the auto-winding is stopped; and

c) determining whether the parameters (current, current slop, speed,speed slope) related to the load is beyond a preset range, if yes, theauto-winding mode is stopped, if no, the auto-winding mode is continued.

As shown in FIG. 9C, the grass trimmer 900 includes a brush motor 901′.In order to realize the switching between the forward rotation and thereverse rotation, a toggle switch 902′ can be used to switch theconnecting methods between the brush motor 901′ and a power supply 903′.And then a main switch 904′ can be operated to start the brush motor901′.

Specifically, a difference between the grass trimmer 910 in FIG. 10A andthe grass trimmer 500 in FIG. 5A is the position of the second operatingelement. In FIG. 10A, the second operating element is disposed on theconnecting rod assembly 912 and close to the trimming head 913.

As shown in FIG. 10B, a second operating element 921 of a grass trimmer920 can be disposed on a first housing 922.

As shown in FIG. 10C, a second operating element 931 of a grass trimmer930 can be disposed on a first housing 932.

The second operating element is disposed close to the trimming head, sothat the user can start the auto-winding mode conveniently when thetrimming line is inserted in the trimming head. Otherwise, the firstoperating element for starting the cutting mode is far from the secondoperating element, so that the user cannot touch the first operatingelement while the auto-winding is running. Similarly, the secondoperating element cannot be touched accidentally while the cutting modeis running.

Referring to FIGS. 11A-11C, a grass trimmer 940 includes a spool 941, ahead housing 942 and line frame elements 943. The spool 941 can bedriven by a motor to rotate. The head housing 942 includes an uppercover 942 a and a lower cover 942 b which are detachable. The headhousing 942 can be rotated relative to the spool 941. The line frameelements 943 can be mounted on the head housing 942, in particular onthe upper cover 942 a in a detachable or undetachable method. When theline frame elements 943 are mounted on the upper cover 942 a, they canbe rotated relative to the spool 941. Further, when the line frameelements 943 are mounted on the upper cover 942 a, they can be rotatedwith the head housing 942 constituted by the upper cover 942 a and thelower cover 942 b synchronously, or with the upper cover 942 a when thelower cover 942 b is detached. Surely, the line frame elements 943 canbe mounted on other part which is able to rotate relative to the spool941.

The line frame elements 943 are formed with line frame structures 943 aallowing the trimming line to pass through and connecting arms 943 b forconnecting the line frame structures 943 a to make the line framestructures 943 a locate on the outside of the spool 941. Specifically,taking the rotation axis of the spool 941 as an axial direction, theconnecting arms 943 b make the line frame structures 943 a locate on theoutside of the spool 941 in a circumferential direction.

When the line frame elements 943 are mounted on the head housing 942 inthe undetachable method, the user can wind the trimming line withoutopening the head housing 942, that is without separating the upper cover942 a and the lower cover 942 b. It is similar to the line windingmethod described above. The trimming line can be passed throughapertures 942 c of the head housing 942. Because the line frame elements943 cannot be rotated relative to the head housing 942, the line framestructures 943 a can be aligned with the apertures 942 c. So, thetrimming line can be passed through the line frame structures 943 a andthen inserted into the spool 941. Thus, when the auto-winding mode isentered, the spool 941 is rotated relative to the apertures 942 c or theline frame structures 943 a so that the trimming line is wound on thespool 941. The advantage is that the user can finish the line windingwhile not having to open the head housing 942.

The user also can realize the line winding in the method of opening thehead housing 942. Firstly, the lower cover 942 b is opened to expose thespool 941 and the line frame elements 943. And then, the trimming lineis passed through the line frame structures 943 a and inserted in thespool 941. When the line winding is ready, the grass trimmer can beoperated so as to realize the relative rotation of the spool 941 and theline frame elements 943. So, the trimming line passes through the lineframe structures 943 a continuously and winds on the spool 941. When theline winding is finished, the lower cover 942 b can be mounted back. Theadvantage is that, it is easy for the user to observe the state of linewinding and control according to the state of line winding.

Alternatively, the line frame elements 943 can be omitted. A whole or apart of the head housing 942 can be made of transparent material, whichcan realize the object of observing the state of line winding as well.

Surely, the line frame elements 943 can be a detachable attachment. Whenit is needed to wind the trimming line, the head housing 942 can beopened, and the lower cover 942 b can be separated. And then, the lineframe elements 943 are mounted on the upper cover 942 a or other partwhich is rotatable relative to the spool 941, for example a housing 944for accommodating the motor. When the mounting is finished, the grasstrimmer is passed through the line frame structures 943 a and insertedin the spool 941. And then the spool 941 is driven to rotate. Surely,the line frame elements 943 can be driven. The trimming line can bewound on the spool 941 through the relative rotation between the spool941 and the line frame elements 943. Then, the line frame elements 943are detached, and the free ends of the trimming line can go out from theapertures 942 c of the lower cover 942 b. And then the lower cover 942 bis coupled with the upper cover 942 a, and the line winding is finished.Or, the upper cover 942 a and the lower cover 942 b can be formed with ahalf of the apertures 942 c respectively. When the upper cover 942 a andthe lower cover 942 b constitute a whole, the whole apertures 942 c isformed. That is the upper cover 942 a and the lower cover 942 b areformed with two recesses respectively. After the line frame elements 943are detached, the trimming line is located in the recesses of the uppercover 942 a or the lower cover 942 b, and then the upper cover 942 a andthe lower cover 942 b are coupled as a whole. The trimming line can passthe apertures formed by the coupling of the upper cover 942 a and thelower cover 942 b. It is easy for the user to make the free ends of thetrimming line go out of the head housing 942 from the inside.

The advantage of the detachable line frame elements 943 is that, for thegrass trimmer with the head housing 942 being capable of detachingentirely or partially, the spool 941 can be exposed through detachingthe head housing 942, and then the line frame elements 943 as anattachment is disposed (the line frame elements 943 may be not mountedon the head housing 942 but mounted on other part which is fixedrelative to the motor, for example the housing of the motor or theguard). And then the spool 941 is driven at a low speed so as to realizethe auto-winding. This can make the previous grass trimmer withoutauto-winding function have the corresponding hardware structure forauto-winding after the line frame elements 943 are disposed. Surely, thespeed of the motor for driving the spool 941should be adjusted so thatthe spool 941 is rotated at a low speed during auto-winding to ensureuser safety.

Referring to FIGS. 11A-11C, the line frame elements 943 are formed withthe line frame structures 943 a. When the auto-winding is performed, theline frame elements 943 can be rotated relative to the spool 941. Theline frame elements 943 are equivalent to simulating the manual windingof the user's hand, and the line frame structures 943 a are equivalentto the fingers for holding the trimming line. So, the line frameelements 943 can be defined as a line holding element for holding thetrimming line so as to make the trimming line rotate relative to thespool. And the line frame structures 943 a can be defined as a lineholding structure which simulates the fingers to hold the trimming lineat a location and allows the trimming line pass through the line framestructures 943 a continuously so as to wind on the spool 941.

As shown in FIG. 11D, a trimming head 940′ includes a spool 941′ and ahead housing 942′, which is similar to the trimming head 940 in FIGS.11A-11C. The difference is that the line frame elements 943 are replacedby the winding pins 943′.

Similarly, the head housing 942′ can be constituted by an upper cover942 a ′ and a lower cover 942 b ′ which are detachable. The winding pins943′ similar to the line frame elements 943 can be detachable orundetachable, which can be mounted on other part being capable ofrotating relative to the spool 941′. The difference is that the windingpins 943′ are not formed with the line frame structures 943 a, butformed with concave parts 943 a ′. The concave parts 943 a ′ can locatethe trimming line going around the concave parts 943 a ′. When thewinding pins 943′ are rotated relative to the spool 941′, they can drivethe trimming line through the friction force so as to realize theauto-winding. So, the winding pins 943′ can be defined as a line holdingelement, and the concave parts 943 a ′ can be defined as a line holdingstructure.

Referring to FIGS. 12A-12B, line frame elements 953 can be acted asfunctional attachments which are independent of a trimming head 950.Line frame elements 953 include a fixing seat 953 c except line framestructures 953 a and connecting arms 953 b. The fixing seat 953 c isconnected with the connecting arms 953 b. When it is needed to wind thetrimming line automatically, an upper cover 952 a and a lower cover 952b of a head housing 952 are separated so as to expose a spool 951. Andthen, the trimming line is passed through the line frame structures 953a and inserted into the spool 951. And then, a motor is started to drivethe spool 951. The spool 951 is rotated relative to the line frameelements 953 so as to realize the auto- winding.

In the embodiment in FIG. 12C, an auxiliary device such as a bracket canbe used to fix the grass trimmer or the spool 951, and an extra motor954 is used to drive the line frame elements 953 to rotate relative tothe spool 951. So, the auto-winding is realized. In this embodiment, therequirements of configuration of the grass trimmer itself is reduced.The auto-winding can be realized through the line frame elements 953acting as separate attachments or a combination of the line frameelements 953 and a corresponding driving device, as long as the headhousing 952 can be opened. And it is no need to change the grass trimmertoo much.

Referring to FIGS. 13A and 13B, a grass trimmer includes a trimming head961, a motor 962 and an energy storing device 963.

The motor 962 is used to drive the trimming head 961 to rotate so as tocut vegetation. The trimming head 961 includes a spool and a headhousing. The spool is accommodated in the head housing. The detailstructure of the trimming head 961 can refer to the trimming head 410 inFIGS. 4A-4D.

The grass trimmer includes a housing 964 for accommodating the motor962. Specifically, the motor 962 is an electric motor having a motorshaft 966 for outputting power.

The grass trimmer has the function of auto-winding. The spool can berotated relative to the head housing so that the trimming line winds onthe spool automatically. Thus, the function of auto-winding is realized.The energy storing device 963 is able to drive one of the spool and thehead housing to rotate relative to the other so as to realize thefunction of auto-winding. The motor 962 rotates to make the energystoring device 963 store energy. Then, the user can control the energystoring device 963 to release energy so as to realize the function ofauto-winding.

Specifically, the energy storing device 963 is disposed within thehousing 964, which is mounted on the top of the motor 962. The energystoring device 963 includes an elastic element 965 which is a coilspring. The coil spring is coupled with the motor shaft 966 on an end.When the motor shaft 966 is rotated, it drives the end of the coilspring to move in a direction indicated by an arrow 967. And the otherend of the coil spring is fixed. At this moment, the coil spring storesenergy. When it is needed to realize the function of auto-winding, thecoil spring retracts to drive the motor shaft 966 to rotate reversely.The motor shaft 966 is connected with the spool or the head housing, soone of the spool or the head housing is driven by the motor shaft 966 torotate relative to the other. Thus, the function of auto-winding isrealized.

A method for controlling the grass trimmer, in particular a method forcontrolling the grass trimmer to wind the trimming line based on theembodiments described above is illustrated as flowing.

As described before, the grass trimmer at least includes the spool, theline holding element and the motor. The spool is used to mount thetrimming line. Specifically, the trimming line can be mounted on thespool in a winding method or other method such as storing. The mainfunction of the line holding element is similar to the function of thefingers against the trimming line while winding the trimming line withhands. That is the line holding element produces a limiting effect tomake the trimming line revolve (taking the spool as a reference) andallow the trimming line to pass the line holding element and wind on thespool. The motor can drive one of the spool and the line holdingelement, so that the line holding element simulates the relative motionpattern of the hand and the spool when mounting the trimming linemanually. That is, the relative rotation is created between the spooland the line holding element.

In is noted that, the line holding element can be constituted by ahousing for accommodating the spool. For example, the head housing canbe acted as the line holding element.

As shown in FIG. 14A, the control method includes: S101 supplying powerto the motor so as to produce a relative rotation between the spool andthe line holding element. More specifically, the control method suppliespower to the motor when the grass trimmer is operated by the user. Thepower supplied to the motor can be electric energy.

Further, the grass trimmer includes a controller and an operatingelement. The controller is used to control whether to supply power tothe motor. When the operating element is activated by the user, thegrass trimmer is controlled by the controller to supply power to themotor. Alternatively, if the operating element is activated again, thegrass trimmer is controlled by the controller to stop supplying power tothe motor.

Further, the grass trimmer includes another operating element. When theoperating element is activated again, the grass trimmer is controlled bythe controller to stop supplying power to the motor. Alternatively, thetwo different operating elements are needed to be pressed to make thegrass trimmer supply power to the motor.

Otherwise, the grass trimmer can be stopped from supplying power to themotor in an automatic method. The operating method includes: S101supplying power to the motor, S102 determining whether the load slope ofthe motor is greater than a preset value, and S103 stopping supplyingpower to the motor. Specifically, the controller determines whether tostop supplying power to the motor according to the load slop of themotor (the slope in the present invention should be considered asincluding mathematic definition which indicates rising tendency such asthe derivative). When the load slope of the motor is greater than thepreset value, the grass trimmer is controlled automatically to stopsupplying power to the motor. When the load slope of the motor isn'tgreater than the preset value, the grass trimmer is controlled to supplypower to the motor continuously. The load state can be determinedaccording to the speed or the speed slope of the motor. When the speedslope is less than a preset value, the controller stops supplying powerto the motor.

When the motor is an electric motor, the current slope of the electricmotor can be used to make a similar judgement control. Specifically,when the current slope of the electric motor is greater than a presetvalue, the controller stops supplying power to the motor.

As shown in FIG. 14B, alternatively, the control method can use a timingmethod. The control method includes: S201 supplying power to the motor,S202 starting timing, S203 determining whether the time satisfies apreset time, and S204 stopping supplying power to the motor.Specifically, when the grass trimmer is controlled by the controller tosupply power to the motor, timing is started. When the time satisfiesthe preset time, the grass trimmer is controlled to stop supplying powerto the motor. when the time does not satisfy the preset time, the grasstrimmer is controlled to supply power to the motor continuously.

Otherwise, the motor can be provided with different power so that thespool and the line holding element can rotate at a first relative speedand a second relative speed respectively. The speed of the motor can bechanged, so the relative rotation speed between the spool and the lineholding element can be changed. However, when the grass trimmer suppliespower to the motor to mount the trimming line, the relative rotationspeed between the spool and the line holding element should be less thanthe rotation speed of the trimming line or the spool while the trimmingline is cutting vegetation.

As shown in FIG. 14C, a method for operating the grass trimmer to windthe trimming line is illustrated as following. The method mainlyincludes the following steps:

S301 providing the grass trimmer.

In this step, the grass trimmer includes the spool for winding thetrimming line, line holding element being formed with line holdingstructure allowing the trimming line to pass through and the motor beingcapable of driving one of the spool and the line holding element.

However, the grass trimmer in this step can be the grass trimmer in theforegoing examples. It is noted that the line holding element isdetachable.

S302 inserting the trimming line.

In this step, the trimming line is associated with the line holdingelement and inserted in the spool. As for associating the trimming linewith the line holding element, it is dependent on the specific form ofthe line holding element and the line holding structure, which can referto the examples described above. Similarly, inserting in the spool canbe understood as inserting in the holes or apertures formed on the spoolor other structure which can limit the ends of the trimming line to holdthe trimming line thereon. This step can make both the spool and theline holding structure act on the trimming line so as to get ready tomount the trimming line.

S303 starting the motor.

The user can start the motor through the operating element or an actionactivating the sensor disposed on the grass trimmer, so that therelative rotation is produced between the spool and the line holdingelement.

S303 switching off the motor.

The user can switch off the motor to make the spool and the line holdingelement be relatively static. However, the controller of the grasstrimmer can be used to determine when to switch off the motor.

Alternatively, the operating element disposed on the grass trimmer canbe triggered to start the motor, and the motor can be switched off bytriggering the operating element once again or by triggering anotheroperating element.

A grass trimmer 1110 of an example of FIGS. 15 a and 15 b includes atrimming head 1111, a driving device 1112 and a connecting rod assembly1113. As shown in FIGS. 15 a to 15 f , the connecting rod assembly 1113includes a connecting rod 1113 a, the trimming head 1111 is disposed ata front end of the connecting rod 1113 a, the driving device 1112includes a motor 1112 a, and the motor 1112 a is an electric motordisposed at a rear end of the connecting rod 1113 a. The grass trimmer1110 includes a first housing 1114 and a second housing 1115. The firsthousing 1114 is disposed at the front end of the connecting rod 1113 a,and the trimming head 1111 is connected to the first housing 1114 . Thesecond housing 1115 is disposed at the rear end of the connecting rod1113 a, the motor 1112 a is mounted to the second housing 1115, at leastpart of the motor 1112 a is disposed in the second housing 1115, and thesecond housing 1115 is also used for mounting a battery pack thatsupplies power to the motor 1112 a. The driving device 1112 furtherincludes a driving shaft 1112 b and a transmission assembly 1112 c. Thedriving shaft 1112 b extends from the rear end of the connecting rod1113 a to the front end of the connecting rod 1113 a. At least part ofthe transmission assembly 1112 c is arranged in the first housing 1114and is connected to the trimming head 1111 to drive the trimming head1111. One end of the drive shaft 1112 b is connected to the transmissionassembly 1112 c, and the other end is connected to the motor 1112 a.

The trimming head 1111 includes substantially the same spool 1111 a andhead housing 1111 b as the grass trimmer 500 in FIG. 5 . The trimminghead 1111 also includes a one-way bearing 1111 c having substantiallythe same structure as that in FIG. 5 . The inner ring of the one-waybearing 1111 c is fixedly connected to the first housing 1114 through aconnecting piece 1111 d, and the outer ring of the one-way bearing 1111c is fixedly connected to the head housing 1111 b.

The trimming head 1111 has a cutting mode and an auto-winding mode. Whenthe trimming head 1111 is in the cutting mode, the motor 1112 a drivesthe spool 1111 a and the head housing 1111 b to rotate synchronouslythrough the drive shaft 1112 b and the transmission assembly 1112 c.When the trimming head 1111 is in the cutting mode, a trimming line 1115is fixed relative to the trimming head 1111, or in other words, thespool 1111 a is fixed relative to the head housing 1111 b. When thetrimming head 1111 is in the auto-winding mode, the motor 1112 a drivesthe spool 1111 a to rotate relative to the head housing 1111 b throughthe drive shaft 1112 b and the transmission assembly 1112 c. When thetrimming head 1111 is in the auto-winding mode, the spool 1111 a rotatesrelative to the head housing 1111 b. The direction of rotation of thespool 1111 a in the auto-winding mode is opposite to the direction ofrotation of the spool 1111 a in the cutting mode. In the auto-windingmode, the head housing 1111 b is fixed, and the one-way bearing 1111 cprevents the head housing 1111 b in the counterclockwise direction. Inthe cutting mode, the one-way bearing 1111 c allows the head housing1111 b to rotate clockwise, and the head housing 1111 b can rotatesynchronously with the spool 1111 a.

The above illustrates and describes basic principles, main features andadvantages of the present invention. Those skilled in the art shouldappreciate that the above embodiments do not limit the present inventionin any form. Technical solutions obtained by equivalent substitution orequivalent variations all fall within the scope of the presentinvention.

What is claimed is:
 1. An operating method for winding a trimming lineof a grass trimmer comprised of a spool allowing the trimming line to bewound thereon, a line holding element being formed with a line holdingstructure allowing the trimming line to pass or bypass, and a motorbeing capable of driving at least one of the spool and the line holdingelement, the operating method comprising: making the trimming line passor bypass the line holding element to be coupled to the spool; andstarting the motor to make the spool and the line holding element rotaterelatively.
 2. The operating method of claim 1, wherein the operatingmethod further comprises: switching off the motor to make the spool andthe line holding element be relatively static.
 3. The operating methodof claim 1, wherein the motor can be started through operating anoperating element disposed on the grass trimmer.
 4. The operating methodof claim 1, wherein the operating method further comprises: switchingoff the motor to make the spool and the line holding element berelatively static, wherein the motor is started through triggering anoperating element disposed on the grass trimmer and the motor can beswitched off through releasing the operating element.
 5. The operatingmethod of claim 1, wherein the operating method further comprises:switching off the motor to make the spool and the line holding elementbe relatively static, wherein the motor can be started throughtriggering a first operating element disposed on the grass trimmer andthe motor can be switched off through triggering a second operatingelement disposed on the grass trimmer.
 6. The operating method of claim1, wherein the operating method further comprises: switching off themotor to make the spool and the line holding element be relativelystatic, wherein the motor can be started through triggering an operatingelement disposed on the grass trimmer and the motor can be switched offthrough triggering the operating element again.
 7. An operating methodfor winding a trimming line of a grass trimmer, comprising: making thetrimming line pass a head housing disposed on the grass trimmer and becoupled to a spool disposed at least partially in the head housing; andstarting a motor to make the spool and the head housing rotaterelatively.
 8. The operating method of claim 7, wherein the operatingmethod further comprises: switching off the motor to make the spool andthe head housing be relatively static.
 9. The operating method of claim7, wherein the operating method further comprises: operating anoperating element disposed on the grass trimmer to switch off the motorto make the spool and the head housing be relatively static.
 10. Theoperating method of claim 7, the operating method further comprises:switching off the motor to make the spool and the head housing berelatively static. wherein the motor can be started through triggeringan operating element disposed on the grass trimmer, and the motor can beswitched off through triggering the operating element again.
 11. Acontrol method for controlling winding of a trimming line of a grasstrimmer comprised of a spool allowing the trimming line to be woundthereon, a line holding element being formed with a line holdingstructure allowing the trimming line to pass or bypass, and a motorbeing capable of driving at least one of the spool and the line holdingelement to make the spool and the line holding element rotaterelatively, wherein the control method comprises: supplying power to themotor to make the spool and the line holding element rotate relatively.12. The control method of claim 11, wherein the grass trimmer suppliespower to the motor when it is operated by a user.
 13. The control methodof claim 11, wherein the motor is supplied power when an operatingelement disposed on the grass trimmer is triggered.
 14. The controlmethod of claim 13, wherein the grass trimmer stops supplying power tothe motor when the operating element is released.
 15. The control methodof claim 13, wherein the grass trimmer stops supplying power to themotor when another operating element disposed on the grass trimmer istriggered.
 16. The control method of claim 13, wherein the grass trimmerstops supplying power to the motor when the operating element istriggered again.
 17. The control method of claim 11, wherein the grasstrimmer stops supplying power to the motor when the load slope of themotor is greater than a preset value.
 18. The control method of claim11, wherein the grass trimmer stops supplying power to the motor whenthe power supplying of the motor lasts for a preset time.
 19. Thecontrol method of claim 11, wherein the motor is supplied differentpower so that the spool and the line holding element are rotated at afirst relative speed and a second relative speed respectively.
 20. Thecontrol method of claim 19, wherein both the first relative speed andthe second relative speed are less than a rotation speed of the spoolwhen the grass trimmer cuts vegetation.